In the related art, throw-away cutting tools such as that described in Japanese Unexamined Patent Application Publication No. 2005-074531 (Patent Document 1) are known as cutting tools used in machining such as grooving and threading. A throw-away tip (cutting insert) of the throw-away cutting tool described in Patent Document 1 has a flat plate shape including two main surfaces with triangular shapes and an outer peripheral surface. Additionally, a recessed portion that engages with a protruding portion of a holder is provided in the outer peripheral surface.
In recent years, a demand has arisen for a cutting insert that can be used for machining where larger loads are applied. With the throw-away tip described in Patent Document 1, the thickness (space between the two main surfaces) of the recessed portion that engages with the holder is narrow and, consequently, there is a possibility that the durability thereof will be insufficient for machining in cases where larger loads are applied.
An object of this aspect is to provide a cutting insert that can be stably locked in a holder even when performing machining where a large load is applied.